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How to handle humidity

Discussion in 'HVAC' started by JPond, Jul 10, 2020.

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  1. JPond

    JPond New Member

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    Hi All,
    I see lots of info and questions around A/C units but I can't fins anything around handling humidity. I got to wondering how do we control humidity in those areas and seasons when it gets high and if we use A/C the humidity just plates out on the glass or furniture or the bulkheads and needs to run off to the bilge. Any one seen any good solutions? Thanks.
  2. Norseman

    Norseman Senior Member

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    AC will somehow remove humidity as the cold air can hold a lot less moisture than warm air: Check the tray below your condenser, it will be full of fresh water, let it drain in the bilge and pump overboard, and add a few drops of chlorine occasionally to keep the bugs at bay.
    Or instal a dehumidifier, it will suck moisture out of the air as well.
  3. Pascal

    Pascal Senior Member

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    “Let it drain in the bilge” ? Hell no... it should drain overboard or in a sump

    A/C removes humidity and keep it dry.
  4. NYCAP123

    NYCAP123 Senior Member

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    Most a/c's have a dehumidify (HU) setting so it's not constantly running and won't turn your boat into a freezer while your away. It's been awhile but if I remember correctly you press 3 buttons at once to pull it up on most of the units I ran.
  5. Norseman

    Norseman Senior Member

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    Sure, do additional plumbing to make the fresh water drain overboard.
    If not, let it go in the bilge and let the bilge pumps push it out.
    On my boat the fresh water drains into a tray, which over flows into the bilge, then gets pumped out.
    On big boats the amount of water and humidity needs its own drainage for sure, but don’t know what size boat the OP was taking about: On my tub the 3 automatic bilge pumps takes care of the excess humidity and it keeps the pumps working and exercised.
  6. NYCAP123

    NYCAP123 Senior Member

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    Totally agree. The amount of condensate is minor. Why put another hole in the boat or plumb into your sump? What's the difference which pump sends it overboard?
  7. leeky

    leeky Senior Member

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    I know you meant evaporator. :)
  8. NYCAP123

    NYCAP123 Senior Member

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    I was just looking at a pic of an A/C control panel similar to what used to be on most boats I ran, and it was a triangle push to turn it to dehumidify, push and hold cool, heat and it's either fan or temp at the same time and HU should show.
  9. Norseman

    Norseman Senior Member

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    Ha, maybe so.
    Will get back to you when I am sober..:cool:
  10. Pascal

    Pascal Senior Member

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    Sorry but that’s not the way to do it. Condensate water is nasty and has stuff growing in it. It needs to be collected and pumped overboard. Not in the bilge. That’s gross. It could be routed to a shower sump if one is nearby. Otherwise, you put in a extra sump...
  11. Pascal

    Pascal Senior Member

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    Easier to set the Tstat a bit higher when you re not on board. Keeps the boat cooler.
  12. NYCAP123

    NYCAP123 Senior Member

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    Fresh water taken from the air is more nasty than the salt water already in your bilge from a dripping shaft, vents, anchor chains, etc.? Why set the Tstat higher? Then it won't turn on by humidity and you'll come back to a damp/moldy boat unless the temp reaches that setting or it'll run constantly on hot days burning electricity and cause that humidity to ice up the unit. Granted it's a problem that doesn't usually happen on larger boats where the compressors are down in the Generator room, but it's a common problem on smaller boats where the units are underneath berths or sofas. Why not just use the dehumidifier setting? Granted a lot of boat owners don't even know about the dehumidifier setting such as the OP.
  13. Capt J

    Capt J Senior Member

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    Here in South Florida, I keep the boats on A/C around 77-78F. Never get any mold. I believe in sending the condensate into a grey water tank and pumping it over......why just move the humidity to the bilge? My bilges on the boats I manage are dry usually. Humidity mode the boat's get too hot inside also damaging furnishings and wood work.
  14. NYCAP123

    NYCAP123 Senior Member

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    If the OP in Mass. set his temp to 77* it'd almost never turn on during the most humid days and nights, just a few days during the height of summer. You'll have a musty boat. Granted that bilges have gotten much drier since the creation of dripless shaft logs, but a bone dry bilge is still the exception rather than the rule and if it happens to be one all the more reason you'd want a little water to kick on your bilge pump once in a blue moon. We're talking condensate. There's not much. Certainly not enough to justify any plumbing or other pumps. I mean if it bothers you go for it, but I see it as a cure looking for a problem.
  15. Norseman

    Norseman Senior Member

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    Because it get pumped out immediately, if you have a good system.
    My bilges are also dusty, I hate standing water in the bilge making a Petri dish under the floor boards.
    (Disclaimer: I only have owned 2 boats with cabin A/C, but worked on quite a few big boats with A/C systems)

    On my present boat I installed a sump-pump with a suction tube much lower than the forward bilge pump could pick up: Upper left hand corner in the picture:

    4F6CE830-74C0-4037-8F27-80FD681F493B.jpeg
  16. Capt J

    Capt J Senior Member

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    The 66' Sunseeker I manage. The A/C's put around 20 gallons of water into the grey water tank per week.
  17. NYCAP123

    NYCAP123 Senior Member

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    That looks like a pretty normal set up where the higher pump would be connected to an alarm, but what is that electrical gizmo near the pumps? Unless it's an optical illusion that looks like it could get submerged and it doesn't look to be made for submersion.
  18. NYCAP123

    NYCAP123 Senior Member

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    Most bilge pump setups I've encountered would kick it overboard at about 1 gallon, about 1". BTW, on that 66 you probably have 4 or 5 A/C units together in one location. So why not direct the condensate into a sump, but on smaller boats you're dealing with units scattered around the boat. Why waste the money on the extra plumbing? Plus if the sump or one of those hoses gets clogged it's going to back up into the salon or stateroom.
    Also in Florida you have constant heat. You need A/C cooling most of the time, and whenever it kicks on you're dehumidifying. So no need to use the HU setting. It's different up north where the OP is from.
    Last edited: Jul 10, 2020
  19. Capt J

    Capt J Senior Member

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    But you always have a wet bilge over many feet of the boat, and that humidity just radiates up and goes back into the boat. Forward bilges on all of the boats that I manage are dry, engine rooms a different story but those are under the aft deck.
  20. NYCAP123

    NYCAP123 Senior Member

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    J you're just looking to argue. If your bilge pump is properly located it's no such thing. This is nonsense. OP just turn on your dehumidify setting and enjoy your dry boat. Good night.
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